Electromagnetic construction and mechanical properties of in-situ Si reinforced Al matrix functionally graded material with Si-rich Si-poor coating structure

How to break through the serious effect of hard and coarse primary Si on the properties of alloy matrix has become a major challenge for motivating the application of high-Si Al alloy piston in automobile lightweight. Herein, we proposed a novel in-situ Si reinforced Al-matrix functionally graded material with Si-rich Si-poor coating structure (Si-rich Si-poor FGM) by controlling the graded distribution of primary Si under rotating magnetic field. The results show that the segregation behaviors of primary Si and intermetallics (Mg2Si, Al9FeNi, Al7Cu4Ni) were directionally controlled during solidification of the multi-component Al-20Si alloy under electromagnetic stirring. The Si-rich Si-poor FGM has successfully combined the high tensile strength (296 MPa for Si-poor region) while meeting the gradient design of the mechanical properties (Vickers/Brinell hardness of Sirich layer was 527%/86% higher than that of Si-poor region). The Si-rich Si-poor FGM shows the superior wear resistance when the temperature is less than 300 degrees C, which meets the limited operating temperature of automotive engine piston. More importantly, the Si-rich Si-poor FGM can be further fabricated into complex parts and constructed continuously, which give rise to the large-scale production of high-Si Al alloy piston in automobile lightweight.